Rust uses https://github.com/rust-community/bors which maintains a linear queue of PRs which can only land after being rebased onto the commits before the PR and subsequently passing tests.

dlang uses several. One notable one is the "autotester" written by Brad Roberts. It's built to ensure that breaking the D compiler (as tested by the test suite) does not result in commits.

It's incredibly useful.

Swift also has a lot of pre-commit CI:

- here is the Jenkins bots page: https://ci.swift.org/view/Pull%20Request/ - example of PR test reporting: https://github.com/apple/swift/pull/6802

In general? Yes, Travis CI seems to be a very popular one. Many folks use Appveyor for Windows support AFAICT.